When using building machines there is a need for substantially unlimited operational reliability and therefore constant availability of the equipment. This results from the interlinking of all the mechanized processes on the building site. Even the shortest unexpected breakdown of a production machine generally leads to further machine downtimes, waiting times for workers and possibly complicated and costly replacement solutions, so that the consequence is that the building work is delayed.
An article in "bd baumaschinendienst", No. 2, Feb. 1988, deals in this connection with modern chain constructions. It is also pointed out that this can affect the versatility of a machine, particularly when, even though an unexpected circumstance does not stop the machine, it is made unsuitable for use under given circumstances. The solution to this is calling in a further suitable machine or, to the extent possible, reequipping the existing machine to meet the new requirements. In this connection the problem of using track-laying vehicles in earthwork engineering and in particular the reequipping of the endless track is discussed and a solution to this problem is given.
In the case of track-laying mechanisms on construction machines, the daily dry cleaning and visual inspection, as well as a complete check for wear and maintenance conditions of all the mechanism components to be performed at somewhat longer time intervals, form part of the obligatory activities of a qualified construction or excavating machine driver. This statement, made in the aforementioned article, shows how difficult it is to use endless track chains, despite their marked robustness. Generally the track travelling gear with the tread, guide and drive rollers are made from steel, as is the chain, which as a rule has a chain part with base plates screwed onto two chain links. In order to withstand the high operating forces, a minimum size must be observed so that such chains have a relatively high mass, i.e., relatively few links on the circumference of the drive wheel. This leads to large base plate dimensions, which are not really desired. On deflecting, guiding or reversing the chain with the screwed on base plates, the latter are strongly spread apart, which has a number of disadvantages. Among these are that when the base plate is set down, i.e., at the time when it is brought from the return strand into the track strand, the plate edge projecting from the circumference strikes the substrate if the latter is flat, or if it is not flat the material therefrom is jammed in the gap which is still open after the reversal and which now closes. In addition, if the material on which the machine is standing is very hard, the machine is raised somewhat on each occasion, resulting in rough running.
In the case of smaller excavating machines, solutions have been sought which could not be used with larger machines. This more particularly applies to rubber chains, which are increasingly being used due to their known advantages. Notable advantages are substantially jointless deflection, a high degree of self-cleaning, better deflection characteristics, tread profiles instead of smooth or webbed base plates, which lead to much lower chain noise levels and much greater compatibility with pavement surfaces.
Thus, e.g., by inserting steel reinforcements in the rubber layer, much as for steel belted tires care, the tractive resistance is considerably increased, but is not as high as that of a steel chain. This is the reason why such advantageous chains have not yet been adopted for even medium size excavators. Unfortunately these advantageous rubber tracks can also not be used for other reasons for certain work, e.g., substrates covered with granite chips, in foundries, on hot slag, etc., so that to be able to cover all circumstances it is necessary to keep available two track-laying vehicles, namely one having rubber tracks for the aforementioned advantages and another with steel tracks where rubber tracks are unusable. This is clearly not an optimum solution from either a cost or logistics standpoint.